Hao Zheng

Summer heat and air pollution may pose a great threat to public health in the context of climate warming, however, their interactive effects on deaths from chronic ischemic heart disease (CIHD) have not been evaluated in existing investigations. This study aims to assess the associations of concurrent heatwave and ozone pollution with CIHD mortality in Chinese population. We carried out a province-wide, individual-level case-crossover study by analyzing 33,770 CIHD deaths occurring in warm season (May–September) across Jiangsu, eastern China, between 2016 and 2019. Spatially resolved estimates of maximum 8-h average ozone concentrations and air temperatures were estimated on case days and control days at the residential address. Heatwave events were defined using multiple temperature thresholds (percentiles 90–97.5) and durations (2–4 days). Conditional logistic regression model was employed to assess the odds ratio (OR) and its 95% confidence interval (CI) of CIHD death associated with heatwave and ozone exposure. Stratified analyses were performed to compare ozone-related risks on heatwave days versus non-heatwave days, and heatwave-related risks on low-ozone days versus high-ozone days. Additive interactive effects were testified using multiple metrics including relative excess odds due to interaction (REOI), proportion attributable to interaction (AP), and synergy index (SI). In the overall population, the odds of CIHD mortality were 1.010 (95% CI, 1.007–1.014) for a 10-µg/m³ rise in warm-season ozone at lag-01 day and ranged from 1.20 (95% CI, 1.15–1.25) to 1.64 (95% CI, 1.54–1.73) for heatwaves under various definitions. Stratified analyses showed intensified ozone-related CIHD risks on heatwave days compared to non-heatwave days and higher heatwave-related risks on high-ozone days than low-ozone days. We observed significant synergistic interactive effects of heatwave and high-level ozone on CIHD mortality (SI > 1), where the excess risk was elevated by 10–19% (REOI > 0) under co-exposure scenarios, and 8–11% (AP > 0) of the odds could be attributed to the additive interaction. Excess fractions of CIHD deaths attributable to heatwave and high-level ozone among overall populations ranged from 4.73% (95% CI, 3.21–6.25%) to 6.43% (95% CI, 4.33–8.45%) under different heatwave definitions. In stratified analyses, we observed similar synergistic effects across age groups and among female subgroups only in multiple heatwave definitions. This study provided novel evidence for the synergistical effects of short-term exposure to heatwave and ozone in elevating CIHD death risk and burden. Our findings highlighted the public health urgency of collective response to climate warming crisis and ambient ozone pollution.

Understanding water intake variation is crucial for assessing human exposure to water pollutants. The correlation between water intake and demographic factors warrants further exploration. A cross-sectional study was conducted to estimate urban water consumption and its associated factors among adults in Wuxi, China, in 2015. The water consumption information was obtained by a 24-h self-report diary over seven consecutive days. A classification and regression tree (CART) analysis was applied to detect how water consumption varied with the demographic variables. Finally, a total of 1188 adults (18–87 years old) were included. The results demonstrated that the median water consumption of the adults was 1525 mL/day in summer and 1217 mL/day in winter. The results of the CART analysis demonstrated that body mass index (BMI) and age were the leading factors that were associated with water consumption in summer and winter, respectively. The water consumption threshold of BMI for men differed from women (23 kg/m² vs. 18 kg/m²) in summer, and the threshold of age for men was also different from women (43 years vs. 21 years) in winter. In conclusion, the findings are useful for accurately assessing human exposure to water pollutants and identifying the high-risk subgroups.

Background: Dehydration due to insufficient fluid intake (IFI) is detrimental to health. This cross-sectional study aimed to assess the fluid intake of urban adults in Wuxi, China, and to identify potential risk factors contributing to IFI. Methods: Adults were selected from the urban area of Wuxi, China, using a multiple-stage random sampling method. The fluid intake information was obtained with a 24-h self-reported diary over seven consecutive days in both summer and winter of 2015. A classification and regression tree (CART) analysis was conducted to detect the potential risk factors associated with IFI. CART is a machine-learning algorithm that portions the data into subsets by threshold. Results: A total of 584 adults aged 18–87 years were included. The results showed that the median (P25–P75) values of daily fluid intake of the participants were 1100 (800–1550) mL in summer and 1000 (750–1300) mL in winter. Women had a higher prevalence of IFI than men in both summer (odds ratio (OR) = 2.683, 95% confidence interval (CI): 1.830–3.934) and winter (OR = 2.636, 95% CI: 1.677–4.142). The results of CART analysis showed that, in summer, BMI < 25 kg/m² (probability: 64.2%) and age < 64 years (probability: 67.4%) were main risk factors of IFI for men, and BMI < 29 kg/m² (probability: 81.6%) and living in C Community (probability: 86.7%) were main risk factors for women. In winter, age < 40 years (probability: 81.8%) and BMI < 20 kg/m² (probability: 94.5%) were identified as main risk factors of IFI for men and women, respectively. Conclusions: Most of the participants living in the study site had IFI. The fluid consumption varied by gender, age, location, and BMI. The findings could be useful for the implementation and optimization of intervention programs by identifying the individuals who may at greater risk of dehydration.